In recent years, digital cameras (image sensing devices) which can sense images and convert them into digital image data by simple operations have been prevalent. When an image sensed by such camera is printed and used as a photo, it is a common practice to temporarily download the sensed digital image data from a digital camera to a PC (computer), execute an image process by the PC, and output the processed image data from the PC to a color printer, thus printing an image.
By contrast, for example, a color print system which allows a digital camera to directly transfer digital image data to a color printer without the intervention of any PC and can print it out, a so-called photo-direct (PD) printer in which a memory card that is mounted in a digital camera and stores sensed images can be directly mounted in the color printer and sensed images stored in the memory card can be printed have recently been developed.
Particularly, in order to directly transfer image data from a digital camera to a printer and print the image data, demands have arisen for standardization of interface specifications between a digital camera of each manufacturer and a printer, the operation method, and the like. One proposal for standardization is a guideline for realizing a DPS (Direct Print System).
However, a printer which directly receives image data from a digital camera and prints the image can also receive print data from a PC or the like in addition to the digital camera and print the data. For this reason, a response to a command from the digital camera may delay due to issuing of a print request from the PC when a pre-procedure for receiving image data between the printer and the digital camera is executed. For example, when a print start request is issued by the digital camera and received by the printer, a status representing that the next command can be accepted changes from “true” to “false”, and the camera is notified of this status. If, however, e.g., a print request is simultaneously issued from a PC, the printer cannot quickly notify the camera of the status change. During this period, the camera may determine that the next command can also be accepted by the printer, and issue the command to the printer in spite of the printer being in busy state.